LONGVIEW, Wash. (AP) — The U.S. Army Corps of Engineers has started a project to replace dozens of steel rods known as king piles in the Columbia River that warn boats and other vessels about the locations of underwater dams.

The $2 million project will replace dozens of 65-foot steel rods marking the end of pile dikes. The dikes are also known as wing dams and are made of alternating vertical timber piles.

Most are at least 100 years old. Officials say about 40 of the 68 pile dikes have been updated so far.